Yes, lots of people watched it, but it never made the cultural impact that The Last Airbender had on society at large. A lot of people remember the movie for it's stunning visuals, and remember the general themes in the movie, but not the actual characters because they weren't particularly memorable.

The Last Airbender had a very compelling story, loveable characters with phenomenal development and it stuck with people.

How many times have you heard someone make a reference to the movie other than talking about it's visual mastery? People use The Last Airbender in everyday conversations.

To demonstrate how many people engage with the fandoms: James Cameron's Avatar has 5,127 fanfiction stories on AO3, and 1678 stories on FFN, and The Last Airbender has 41,627 fanfics on AO3, and 47,680 on FFN.